The invention relates generally to seal devices and, more particularly, to sealing devices in combinations for use in shaft bearings.
In conventional shaft bearings such as pillow blocks and similar large size shaft bearings, it is a common practice to seal the bearings between the shaft and its supporting housing with a labyrinth-type seal which, when properly lubricated, performs rather effectively to exclude foreign matter and which permits a purging action to take place to expel dirt and moisture from the inner chamber of the bearing housing while the bearing is in operation and/or while the bearing is being lubricated.
A labyrinth seal normally comprises two or more interrelated annular grooves and ribs formed on a shaft and in the adjacent surfaces of the housing. While this type of seal is fairly effective for small bearings, such type of seal often fails to perform satisfactorily for large bearings in that the lubricant injected in the housing usually settles into a sump or recess in the bottom of the housing. This settling of the lubricant prevents the filling of the annular grooves in the seal thus permitting the free flow of moisture and abrasive matter through the seal and into the bearing housing. In addition, since the lubricant from the housing fails to fill the grooves of the seal, effective purging operations to remove dirt from the seal are not possible.
In an effort to prevent the ingress of moisture and foreign matter into the bearing housing in large bearings, a structurally independent auxiliary seal is sometimes used externally of the labyrinth seal. The auxiliary seal is usually a V-ring type mounted on and rotatable with the shaft. As known in the art, the V-ring type is formed with a flexible lip adapted to seat on an annular radial surface of the housing. This type of seal, however, is not fully effective in that as the shaft moves endwise during operation, the lip may become fully displaced from the radial sealing surface, thereby providing a space through which moisture and dirt can reach and pass through the labyrinth seal.
In the prior art there are a number of variations to known sealing devices disclosed which attempt to correct one or more disadvantages inherent in such devices for use in shaft bearings. In U.S. Pat. No. 4,575,265, assigned to the same assignee as is the present application, a V-ring type seal is disclosed as having a lip in sealing contact with the surface of a separate ring attached to the inner surface of the bearing housing. The V-ring seal is mounted directly on the inner race for the bearing for rotation therewith and does not provide a sealing relationship with the shaft supported by the bearing.
In U.S. Pat. No. 4,153,259, a V-ring seal is utilized in a manner in which it is tightly placed upon a sleeve which, in turn, is supported on a shaft. The seal includes a lip portion in sealing engagement with a wall surface of the bearing housing. Auxiliary sealing rings are also utilized in conjunction with the V-ring seal but these are also mounted upon the same sleeve. This arrangement experiences disadvantages which result when there is no positive sealing engagement with the shaft, and when there is no interaction between the seal devices.
In U.S. Pat. No. 4,106,781, a press-fitted cylindrical wear sleeve formed to contain a complex V-ring type seal having multiple sealing lips is adapted to be inserted into the annular opening in a bearing thereby permitting the simple installation of the sealing device. The disadvantage in the use of this type of seal device is that the cylinder itself may be the source of movement of contaminants into the bearings.
The use of a V-ring seal which also forms a simple labyrinth seal is disclosed in U.S. Pat. No. 4,054,335. The V-ring seal is not directly contacting the supported shaft and the device which is utilized as a labyrinth seal comprises a synthetic material. The lip for the V-ring seal is in sealing engagement with a flexible ring thus presenting an environment wherein elevated temperatures produced during the operation of the bearing may effect different expansion characteristics to the flexible ring and labyrinth seal which, in turn, may affect the sealing capabilities of these elements.
In the U.S. Pat. Nos. 3,994,545, 3,858,950, and 3,504,917 and the Australian Pat. No. 153,472, various shapes of flexible sealing devices are disclosed which utilize sealing lips engageable with surfaces provided in the bearings to be sealed.
None of the patents discussed above disclose multiple sealing connections or relationships whereby the different and unique characteristic of each sealing device can be integrated so that high efficiency is attained in sealing a shaft bearing. In the present invention, it is recognized that each specific type of sealing device has a unique characteristic of its own which offers an advantage not inherent in other types of sealing devices so that when a variety of different sealing characteristics are combined, optimum performance of sealing is possible. For very large shaft bearings or those which experience wide vibrations and shaft displacements coupled with extreme variations in temperature during shaft rotation within the bearing, and for use in environments having high humidities and aerial contaminants, there is the need to bring together all of the specific advantages that each type of sealing characteristic provides.
The present invention brings together at least three and preferably four sealing characteristics, each of which contributes to the combined effect of all to produce a high efficiency, improved sealing arrangement for a shaft bearing. The high efficiency seal system of the present invention combines at least a dynamic face rubbing lip seal, a static shaft seal and a flinger seal, and preferably also a labyrinth seal. With this arrangement, the sealing system takes advantage of all of the seal types to form a sealing system which has very large misalignment capability but still provides superior sealing protection against dirt and moisture.
The present sealing system includes a V-ring seal tightly mounted on a shaft to form a positive static seal along the shaft, the V-ring having a lip which is arranged to contact a radially oriented smooth surface such as a portion of the bearing housing, thereby providing a dynamic contact seal as the lip rubs on the housing surface during rotation of the shaft. The sealing system also includes a seal ring into which a quad-ring, o-ring or the like seal is installed for supporting the seal ring, the quad-ring seal serving as a secondary static shaft seal. The quad-ring is tight on the shaft and rotates therewith as does the seal ring. With the seal ring riding on the quad-ring, the same will rotate with the shaft and serves as a flinger seal thereby helping to direct contaminants away from the shaft and ring seal. The specific structures for the seal devices are interrelated, and cooperate to provide optimum efficiency while utilizing a minimum of parts and in an arrangement which permits easy and simply installation.
It is therefore one of the principle objects of the present invention to seal a shaft in a bearing in a manner which permits the effective purging action of the bearing during operation and lubrication and yet which positively seals the bearing from the ingress of foreign material, both during operation and during cooling of the bearing when it becomes inoperative.
Another object of the invention is to utilize a seal system which provides a plurality of sealing characteristics or types in combination between the shaft and the internal structure of the shaft bearing, which permits the flow of lubricant, dirt and moisture outwardly from the bearing structure and yet prevents the ingress of dirt and moisture into the bearing structure.
A further object of the invention is to seal a bearing utilizing structure which are relatively simple in construction and operation and which result in little or no wear between moving parts and hence provide a long, trouble-free lift with little or no servicing or other intention to maintain the seal in optimum operating condition.
Still another object of the invention is to provide a seal for shaft bearings which is particularly adapted for large bearings, and which functions effectively irrespective of the large displacement and vibrations during operations of the bearing.
Other objects and advantages of the present invention will become apparent from the foregoing description taken in conjunction with the accompanying drawings wherein: